1. Field of the Invention
This invention relates to a video signal recording and/or reproducing system, and more particularly to a video signal recording and/or reproducing system available for automatic head scan tracking.
2. Description of the Prior Art
In video tape recorders (VTR), video signals are recorded on a magnetic tape in the form of a plurality of recording tracks which extend across the longitudinal direction of the tape and are arranged in parallel with one another with a predetermined unrecorded area, called the guard band between adjacent tracks.
In such VTR, the recording tracks formed by the rotary magnetic head are not always linear, and are sometimes deformed due to elongation of the tape. Accordingly, when the video signals recorded on the magnetic tape by one VTR are reproduced from the same magnetic tape by another VTR, it is difficult to made the rotary magnetic head scan the centers of the recording tracks, and there often occur some tracking errors with which the levels of the reproduced signals fluctuate, and there occurs crosstalk from the adjacent tracks. The quality of the reproduced signal is deteriorated.
For this reason, there has been proposed such a method in which the rotary magnetic head is moved by an electromechanical transducer in the direction to intersect the longitudinal direction of the tape to carry out an automatic head scan tracking. With this method, a tracking error signal is provided by deflecting intentionally, with the transducer, the magnetic head by a small amount in each direction from the track center in a sinusoidal manner so as to create a carrier amplitude modulation of a known frequency and phase. This tracking error signal is fed back to the transducer to complete a tracking servo loop. Accordingly, even if the recording tracks are curved, the reproducing head can scan the recording tracks. With this method, however, the carrier amplitude modulation is always created in a reproduced signal, so that the phase of the reproduced signal is changed thereby, and especially noticeable is the phase error in the chrominance signal caused by the phase change in the reproduced signal. Further, the apparatus for achieving the above method becomes complicated in construction.
According to the proposed method, in the VTR of the type in which video signals are recorded on the magnetic tape so that the guard band is narrow or zero in width, the crosstalk components are included in the reproduced video signals by the intentional deflection of the magnetic head. The quality of the reproduced video signals is deteriorated. Accordingly, the proposed method is not practical.